“That would have been grand by night,” shouted the doctor.
“It was grand now,” replied Sir John.
“Well, I think we had better turn back,” said the doctor. “There is no doubt about its being molten fire below here, for the heat gets fiercer. Look.”
He had been resting on the climbing pole he brought up with him, and found that the end had gone down a couple of feet, while as he drew it out the point was charred and smoking.
This induced Sir John and Jack to do the same, and theirs were burnt as well.
“Yes, get back at once!” shouted Sir John in startled tones. “Quick, all of you; our weight is acting upon the ashes, and they are gliding down with us.”
“Hi! look out below, gen’lemen,” shouted Lenny from the edge, “that there’s bending like thin ice.”
The warnings were none too soon, for as the pair turned sharply and began to climb back, it was quite plain that though the blocks of stone about lay or half floated upon the ash-covered surface, any further weight was sufficient to produce a change, and before they had taken many steps, one huge mass not twenty yards from Sir John was seen to be sinking slowly, then faster and faster, and disappeared through the ashes, which changed rapidly to a shimmering fluid, and sent forth a terrible heat.
“Don’t hurry—open out slowly so as to spread the weight!” cried Sir John; and the doctor and Ned obeyed; but Jack saw that at every step his father’s feet sank lower, and that his alpen-stick gave him no support, but went right in.
“Do you hear me, Jack?” shouted Sir John.